Water usage continues to increase in seemingly all sectors of society, including industrial, commercial, agricultural and consumer areas. This has led to concern over water shortages even at the national level. Thus, it is undisputed that water usage must become more efficient to avoid shortages and conflicts over water rights.
Although there have been proposed various types of consumer irrigation systems which include a clock or some type of timing device which automatically starts and stops the flow of water in the irrigation system (e.g., for use in watering a lawn), such irrigation systems operate only in accordance with the manner in which they have been pre-set. That is, the timing device is programmed to start and then stop the flow of water at very precise, predetermined times. The need for water, however, varies from time to time and is to that extent independent of the operation of the irrigation system. Thus, at best, the effectiveness of such irrigation systems is only as good as the ability of the owner to predict the precise need for water in the soil.
One type of device which has been used previously to measure need for added moisture in soil is known as a tensiometer. Such a device includes a tube filled with water and inserted into the ground. At the top of the tube there is a vacuum gauge. As water from the tube diffuses into the soil a vacuum is created at the top of the tube. The vacuum gauge can be adapted to trip a switch, for example, to activate an irrigation system.
Another type of device used to determine moisture content in soil includes a gypsum block having two electrodes inside of it and wires attached to the electrodes. The device is buried in the ground with the wires being accessible at the top of the ground (e.g., in a box). A portable ohm meter (powered by a DC battery) may be temporarily connected to the wires in order to measure the resistivity of the soil. The resistivity measurement obtained is compared to a chart or guide in order to determine how much water should be applied to the soil.